A frame straightening method

Abstract

The application discloses a frame correction method, comprising: forming and measuring profile deviation, making rubber pads, initially setting the total thickness of the rubber pads, correcting and measuring the profile deviation, if the absolute value of the deviation is less than the tolerance epsilon, the correction is ended, otherwise, the total thickness of the rubber pads or the direction of the rubber pads is changed as needed. The application sets rubber pads on the opposite side of the springback direction of the initial forming of the part, and changes the number or direction of the rubber pads according to the correction result each time, so as to realize the soft compensation of the mold profile, and then compensate the springback of the part, so that the part after correction meets the design requirements. The application does not need to repair the mold, reduces the processing cycle and cost, does not use a hammer to strike the surface of the part, the surface of the part is smooth without local depression, the rubber pads are easy to obtain and can be reused, and the method is economical when producing similar cross-section multi-specification, single-piece small-batch parts.

Description

Technical Field

[0001] This invention belongs to the field of sheet metal part shaping technology, specifically relating to a frame shaping method. Background Technology

[0002] Aerospace sheet metal frames are mostly made of aluminum alloy, typically 2-6mm thick, and are either thin or medium-thick plates. Even with the same plate thickness, there are multiple sizes, resulting in different central angles. For frames with the same plate thickness, cross-section, and radius, parts with different central angles will have different chord heights, varying degrees of plastic deformation, and different springback angles. The molds used for die-pressing aerospace sheet metal parts are usually integral steel molds. After mold manufacturing, the shape is fixed, leading to significant springback during trial molding, especially for medium-thick plate parts. This makes it difficult to form the parts perfectly in one go, often requiring mold rework. For single-piece or small-batch production, mold rework is costly, time-consuming, and uneconomical. Furthermore, for general-purpose molds—frames with the same plate thickness, cross-section, and radius but different rotation angles—one mold cannot compensate for the springback of all frame sizes to an ideal state. This results in a large workload for manual shaping with hammers in subsequent processes, leaving numerous hammer marks on the part surface and poor surface quality. Some sheet metal frames have a Z-shaped cross-section. When adjusting the radius, the generatrix will deteriorate, and when adjusting the generatrix, the radius will deteriorate again, resulting in a large workload. The thicker the material, the greater the workload. Summary of the Invention

[0003] The purpose of this invention is to achieve rapid and damage-free shaping of a Z-shaped cross-section frame with the same plate thickness, cross-section, and radius but different central angles, without reworking the mold or damaging the surface quality with a hammer. To solve the above-mentioned technical problems, this invention provides a frame shaping method.

[0004] A frame correction method includes the following steps:

[0005] S1: Forming and measuring surface deviation. The blank is pressed and formed, and the deviation between the surface and the theoretical shape is measured and recorded using process equipment and measuring tools, including the deviation in the arc length direction and the generatrix direction.

[0006] S2: Make rubber pads, select the thickness of the rubber pads and cut the length and width of a single rubber pad according to the size of the area to be padded on the part;

[0007] S3: Initially set the total thickness of the rubber pad, and change the number of rubber pad layers to the target thickness. The target thickness should be larger than the shape deviation of the first forming.

[0008] S4: Correction and measurement of surface deviation. Place the rubber pad on the area of ​​the part to be corrected, run the press to correct it, and measure the deviation between the surface and the theoretical shape. If the absolute value of the deviation is less than the allowable tolerance ε, the correction is completed; otherwise, proceed to S5.

[0009] S5: Change the total thickness of the rubber pad or the direction of padding as needed. Based on the surface deviation results after the correction, change the number of rubber pad layers or the direction of padding, and then switch to S4.

[0010] As a preferred embodiment, in step S1, a press and a forming die are used to press and shape the blank.

[0011] As a preferred method, in step S1, the deviation in the arc length direction is measured at the center line of the width symmetry of the part, and the deviation in the generatrix direction is measured at the center line of the length symmetry of the part and the generatrix of the cross sections at both ends, and the average value of the three is taken.

[0012] As a preferred embodiment, the thickness of the individual rubber pad in step S2 should be as small as possible compared to the allowable part shape deviation value.

[0013] As a preferred method, the rubber pads produced in step S2 should be prepared in a certain quantity as needed.

[0014] As a preferred approach, the thickness of the rubber pad produced in step S2 should not exceed the allowable part shape deviation value by too much.

[0015] As a preferred method, if the deviation result in step S5 is a positive deviation, then the number of rubber pads is increased by 2, and the increased thickness is greater than the surface deviation; if the deviation result is a negative deviation in a certain direction, then the direction of adding the rubber pads on the part in that direction is reversed, and the number of rubber pads is reduced.

[0016] Further preferably, the direction of the padding for the positive or negative deviation is fixed.

[0017] The beneficial effects of this invention are:

[0018] By placing a rubber pad on the opposite side of the initial springback direction of the part, and changing the number or direction of the rubber pads according to the results of each forming, soft compensation of the mold surface is achieved, thereby compensating for the springback of the part and ensuring that the part meets the design requirements after forming. This invention eliminates the need for mold repair, reducing processing cycle and cost. It also avoids hammering the part surface, resulting in a smooth surface without local depressions. The rubber pads used are readily available and reusable. This method is economical for producing single-piece, small-batch parts with similar cross-sections and multiple specifications. Attached Figure Description

[0019] Appendix Figure 1 A flowchart of the frame alignment method provided by the present invention;

[0020] Appendix Figure 2 The main view is a schematic diagram of the principle of the frame straightening method provided by the present invention;

[0021] Appendix Figure 3 A schematic diagram of the frame straightening method provided by the present invention, view A;

[0022] Appendix Figure 4 This is a schematic diagram showing the positive deviation in the arc length direction of the board frame;

[0023] Appendix Figure 5 This is a schematic diagram showing the positive deviation of the generatrix direction of the plate frame.

[0024] In the figure, 1 is the board frame, 2 is the rubber pad, 3 is the theoretical shape of the board frame in the arc length direction, 4 is the shape of the board frame after springback in the arc length direction, 5 is the theoretical shape of the board frame in the generatrix direction, and 6 is the shape of the board frame after springback in the generatrix direction. Detailed Implementation

[0025] To make the technical means, creative features, achieved objectives, and effects of this invention readily understandable, embodiments of the invention are provided below for detailed description. It should be noted that these embodiments are only for further illustration and should not be construed as limiting the scope of protection of this invention. Those skilled in the art can make non-essential improvements and adjustments based on the content of this invention.

[0026] Example 1:

[0027] like Figures 1 to 5 As shown, after the sheet frame 1 is formed, it usually experiences positive springback, resulting in a positive deviation. Specifically, the radius of curvature of shape 4 after springback in the arc length direction is larger than that of the theoretical shape 3 in the arc length direction, and the shape 6 after springback in the generatrix direction is smoother than the theoretical shape 5 in the generatrix direction. A press with rubber pad 2 is needed for reshaping. The reshaping process includes the following steps:

[0028] The first step is forming and measuring surface deviations. A press and forming mold are used to press and shape the blank. After the pressure is released, the sheet frame 1 is removed. Using process equipment such as arc templates and section templates, as well as measuring tools such as calipers and feeler gauges, the deviations between the surface and the theoretical shape are measured and recorded, including deviations in the arc direction and generatrix direction. The templates, whether internally cut or externally cut, should be prepared according to the dimensions required by the design. Deviations in the arc direction are measured at the symmetrical centerline of the part's width, and deviations in the generatrix direction are measured at the symmetrical centerline of the part's length and at the generatrix of the sections at both ends. The average of these three measurements is taken.

[0029] The second step is to manufacture the rubber pads, including selecting the thickness of rubber pad 2 and cutting the target rubber pads to the length and width according to the dimensions of the area to be padded on the board frame 1, and initially preparing a certain quantity. The thickness of the rubber pad 2 should not exceed the allowable part shape deviation value by too much, and the width and length are as follows... Figure 2 , Figure 3 As shown, the specified quantity is set as needed and can be increased later.

[0030] The third step is to initially set the total thickness of the rubber pad 2 by overlapping multiple layers of the rubber pad 2 until the target thickness is reached. The target thickness is larger than the shape deviation of the first forming.

[0031] The fourth step is to calibrate and measure the surface deviation. Place the rubber pad 2 on the area of ​​the part to be calibrated, run the press to calibrate, and measure the deviation between the surface of the plate frame 1 and the theoretical shape. If the absolute value of the deviation is less than the allowable tolerance ε, the calibration is complete.

[0032] Example 2:

[0033] like Figures 1 to 5 As shown, after the sheet frame 1 is formed, it usually experiences positive springback, resulting in a positive deviation. Specifically, the radius of curvature of shape 4 after springback in the arc length direction is larger than that of the theoretical shape 3 in the arc length direction, and the shape 6 after springback in the generatrix direction is smoother than the theoretical shape 5 in the generatrix direction. A press with rubber pad 2 is needed for reshaping. The reshaping process includes the following steps:

[0034] The first step is forming and measuring surface deviations. A press and forming mold are used to press and shape the blank. After the pressure is released, the sheet frame 1 is removed. Using process equipment such as arc templates and section templates, as well as measuring tools such as calipers and feeler gauges, the deviations between the surface and the theoretical shape are measured and recorded, including deviations in the arc direction and generatrix direction. The templates, whether internally cut or externally cut, should be prepared according to the dimensions required by the design. Deviations in the arc direction are measured at the symmetrical centerline of the part's width, and deviations in the generatrix direction are measured at the symmetrical centerline of the part's length and at the generatrix of the sections at both ends. The average of these three measurements is taken.

[0035] The second step is to manufacture the rubber pads, including selecting the thickness of rubber pad 2 and cutting the target rubber pads to the length and width according to the dimensions of the area to be padded on the board frame 1, and initially preparing a certain quantity. The thickness of the rubber pad 2 should not exceed the allowable part shape deviation value by too much, and the width and length are as follows... Figure 2 , Figure 3 As shown, the specified quantity is set as needed and can be increased later.

[0036] The third step is to initially set the total thickness of the rubber pad 2 by overlapping multiple layers of the rubber pad 2 until the target thickness is reached. The target thickness is larger than the shape deviation of the first forming.

[0037] The fourth step is to calibrate and measure the surface deviation. Place the rubber pad 2 on the area of ​​the part to be calibrated, run the press to calibrate, and measure the deviation between the surface of the plate frame 1 and the theoretical shape. If the absolute value of the deviation is not less than the allowable tolerance ε, then proceed to the fifth step.

[0038] Step 5: Change the total thickness or direction of rubber pad 2 as needed. Based on the surface deviation results after the board frame 1 is shaped, change the number of layers or direction of rubber pad 2, and then proceed to step 4.

[0039] If the deviation result is a positive deviation, the number of rubber pad 2 layers is increased, and the increased thickness is greater than the surface deviation. If the deviation result is a negative deviation in a certain direction, the direction of adding rubber pad 2 on the part in that direction is reversed, and the number of rubber pad 2 layers is reduced. The direction of adding shims for positive or negative deviations is fixed. The above-mentioned reversal of direction does not mean that the direction of adding shims for negative deviations will become the direction of adding shims for positive deviations after one or more reversals.

[0040] It should be noted that, for the sake of simplicity and clarity, the press and forming mold are not shown; their structure and assembly relationships are readily apparent to anyone skilled in the art. Furthermore, the method of this invention is not only applicable to sheet metal frames, but also to profile frames with similar cross-sections; those skilled in the art should be able to easily adapt this method to the shaping of profile frames.

Claims

1. A method for frame alignment, characterized in that, Includes the following steps: S1: Forming and measuring surface deviation. The blank is pressed and formed. The deviation between the surface and the theoretical shape is measured and recorded using process equipment and measuring tools. This includes the deviation in the arc length direction and the generatrix direction. The deviation in the arc length direction is measured at the center line of the width symmetry of the part, and the deviation in the generatrix direction is measured at the center line of the length symmetry of the part and the generatrix of the cross sections at both ends. The average value of the three is taken. S2: Make rubber pads. Select the thickness of the rubber pad and cut the length and width of a single rubber pad according to the size of the area to be padded on the part. The thickness of the single rubber pad should be as small as possible smaller than the allowable part shape deviation value in the design. The thickness of the rubber pad made should not be too much larger than the allowable part shape deviation value in the design. S3: Initially set the total thickness of the rubber pad by changing the number of rubber pad layers to the target thickness. The target thickness should be larger than the shape deviation of the first forming. S4: Shaping and measuring surface deviation. Place the rubber pad on the area of ​​the part to be shaped, run the press to shape it, and measure the deviation between the surface and the theoretical shape. If the absolute value of the deviation is less than the allowable tolerance ε, the shaping is complete; otherwise, proceed to S5. S5: Change the total thickness or shim direction of the rubber pad as needed. Based on the surface deviation results after the correction, change the number of rubber pad layers or the shim direction, and then switch to S4. If the deviation result is a positive deviation, increase the number of rubber pad layers, and the increased thickness should be greater than the surface deviation. If the deviation result is a negative deviation in a certain direction, reverse the shim direction of the rubber pad on the part in that direction and reduce the number of rubber pad layers.

2. The frame alignment method according to claim 1, characterized in that: In step S1, a press and forming mold are used to press and shape the blank.

3. The frame alignment method according to claim 1, characterized in that: The rubber pads produced in step S2 should be prepared in a certain quantity as needed.

4. The frame alignment method according to claim 1, characterized in that: The direction of the padding for the positive or negative deviation is fixed.

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